Antirrhinum striatum/pseudomajus
One of the most dynamic systems at present is Antirrhinum striatus/pseudomajus. The two species are thought to have hybridized in this area (Espinosa, Girona, Spain), with pollinators playing their part in the hybridization.
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The researcher always assumes that two closely related species interbreed, thus creating a zone with hybrid forms. So far, so good. - Now, this zone is altering. And that within ten to fivteen years.
This dynamic raises doubts about whether this is the outcome of hybridization and gene flow.
For a recent study, see this pathbreaking and excellent thesis of
- asymmetric distribution - el/el deficit
The summary of the analyses presented in this thesis demonstrates that the genetic structure of plant individuals in this transition zone between Toses and Planoles needs further investigation to unravel completely.
Due to the exponentially growing amount of genomic information on the Internet (https://www.ncbi.nlm.nih.gov/, https://www.ebi.ac.uk/ena/browser/home) it is now possible to use this information source for independent genetic analyses.
ROS1-locus
STR 53,016,900 Vers.3 Amajus
ROS1 and its alleles can differ primarily in the number of CGGG repeats in the promoter region, the length of TAT repeats in the intron, and the presence of distinct motifs at the C-terminal end. We propose that a straightforward algorithm could be used to create an activated ROS1-Myb from an inactive ros1-MYB.
The hybrid origin model already exists. We can also offer a transit model to explain the variety of color phenotypes seen in the transition zones. In this model, STR (short tandem repeats) within MYB introns that spontaneously change their length may gradually bring about the new pseudomajus shape. Note: In-between forms do not strictly follow the Mendelian LAW.
A comparison of short tandem repeats (STRs) and C-motifs, along with Fst divergence within the ROS-EL area, reveals that all TATA-repeats and C-motifs align closely with the observed peaks and troughs in pseudomajus and striatus varieties of Antirrhinum majus.
Additionally, these repeats are also geographically correlated.
That means that the TTATTA-STR ROS1 is observed in the West in yellow striatum plants, while the TAATAAT-string ROS1 is seen in red pseudomajus in the East. It's a gradual replacement from one type to the other following the West-East route.
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SULF-locus Chr4:34,600,850-34,603,200 Amajus.IGDBv3.chr.fasta
Light green, grey, red, and light blue DNA areas are all needed for a functional SULF allele. When the red or other parts are missing, the gene remains in the status of an inactive sulf-allele. A transposon might be the reason for a spontaneous switch over to either side (SULF or sulf status).
Different activation states of SULF/sulf in yellow striatum population (left), still yellow colored Y1 population (middle), and magenta colored population (right). The grey and green parts are reduced but not completely absent in striatum populations. Full blue, grey, and green parts result in SULF. Absent grey and green parts result in sulf (N=50).
A well-studied molecular element is located at the SULF locus on Chromosome 4. When active, SULF restricts aurone synthesis in the petals, either locally or globally. This element appears to function as a switch, activating or deactivating depending on structural or evolutionary needs.
In summary, ROS1*, ROS2, EL, and SULF can all be modified from a passive recessive state to an active state with minimal effort from a molecular genetic perspective. One can find an algorithm that transforms those inactive alleles into active alleles. Furthermore, the changes at these four loci can occur largely independently of one another.
*Note: In a molecular genetic context, ROS1 indicates that this MYB is upregulated and no repressor is active; ros1 signifies that the MYB is downregulated or not in a functional state.
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